House dust mites are important as a major causative factor of allergic diseases such as atopic bronchial asthma. Traditionally, hyposensitization therapy has been the most important radical therapy for allergic diseases, in which patients are hyposensitized by administration of allergen, the substance which causes allergy. Specifically, in diseases in which antigen identification is easy, such as pollinosis and insect allergy, hyposensitization therapy can be said to have already been highly valued. This therapy, however, necessitates administration of a safe therapeutic antigen because it involves a risk of anaphylaxis due to allergen.
Two mite species, namely Dermatophagoides pteronyssinus and Dermatophagoides farinae, are reported to play a major role as house dust mite allergens in mite allergic diseases [J. Allergy: 42, 14-28 (1968)]. The major mite allergen which have so far been reported include glycoproteins with a molecular weight of 24 to 28 kD (pI 4.6 to 7.2) and/or proteins with a molecular weight of 14.5 to 20 kD (pI 5 to 8.3), both contained in mite feces and/or mites [e.g. J. Immunol.: 125, 587-592(1980)/J. Allergy Clin. Immunol.: 76, 753-761(1985)/Immunology: 46, 679-687 (1982)/Int. Arch. Allergy Appl. Immunol.: 81, 214-223(1986)/J. Allergy Clin. Immunol.: 75, 686-692(1985)].
On the other hand, the present inventors reported the presence of components which exhibit specific reactivity to serum IgG of mite asthmatic patients and which induce leukocyte histamine release in mite asthmatic patients in fractions with higher molecular weight and those with lower molecular weight in comparison with the above-mentioned major mite allergens [The Annual Meeting of the Japan Society of Agricultural Chemistry: 62, 411 (1988)]. These components, however, remained to be purified to a degree such that they can be used as antigens for hyposensitization therapy.
Mite allergic diseases have been diagnosed mainly on the basis of inquiry in combination with skin reaction tests using a house dust extract and/or mite extract in most cases, with measurements of serum IgE antibody titer (relative values) taken by the RAST method used in only a very few cases; it has been very difficult to make direct diagnoses of mite allergic diseases.
Traditionally, house dust extract solutions have been used for hyposensitization therapy for bronchial asthma involving house dust mites as specific antigens; however, their dose is subject to extreme limitation and their therapeutic effect is extremely low, since they are very indefinite in chemical composition and contain a wide variety of impurities which may induce anaphylaxis. Therefore, from the viewpoint of efficacy and safety, it is desired that a valuable antigen for hyposensitization therapy will be developed.
Also, it is important to make quick and accurate diagnoses of mite allergic diseases in appropriate treatment of mite allergic diseases; a new diagnostic system is expected to be well established.